For connecting, branching off and plugging of cables, in particular underground cables, screw connectors, cable connecting clamps or cable lugs are conventionally used, into which shearable fasteners are inserted for fixing or contacting of the conductors, respectively.
A shearable fastener usable for multi range cable connectors is described in the applicant's patent EP 0 984 176 B1. The biggest conductor cross section is clamped with the biggest turning moment respectively the biggest force. Smaller cross sections are installed by using a reduced force.
However there are two major disadvantages of the above mentioned conventional fastener concerning its function. Firstly, for the installation of the fastener two different tools may be necessary: an Allen key for big conductor cross sections and a hexagon socket wrench for smaller conductor cross sections. This implies that the installation can be cumbersome for a technician, particularly when installing the shearable fastener in places with limited space and/or at difficult angles. Secondly the range of conductor cross sections of the screwing connector is usually limited by the length of the Allen key (commonly 19 mm). Therefore certain types of shearable fasteners cannot be installed for certain types of conductors thus generating a limiting factor for the applicability of the shearable fastener.
GB-2 295 871-A describes a screw shank for exerting a clamping force on one of a series of objects of known sizes, e.g. an electrical conductor received in a connector. The screw shank comprises an external screwthread so that rotation of the shank by drive means including a drive rod which is inserted into an internal recess of the screw shank screws it into the conductor. The shank is formed with a series of weakened sections spaced along the screwthread such that when a predetermined torque is reached, one of the weakened sections lies in the plane of the surface of the article to encourage the shank to shear in that plane. This device has the drawback that the shearing plane is defined by the length of the drive means: firstly the extension into the internal recess, secondly the outer extension of the skirt. Therefore, if a soft conductor with a small cross section is to be clamped, the screw shank will extend very far into the bore while the drive rod's extension into the internal recess of the screw shank is limited by its construction, i.e. it will stay in a plane which is quite far away from the appropriate shearing plane since it doesn't move forward with the screw shank but only rotate in a final position. Thus with this screw shank it is likely that the shearing takes place in the wrong shearing plane exerting a wrong clamping force on the conductor.